Stripline or waveguide lasers are known from German Published, Non-Prosecuted Application DE 37 29 053 A1, corresponding to U.S. Pat. No. 4,939,738. The construction mentioned above is described in Published European Application No. 0 477 865. There, bars with very low temperature expansion coefficients are rigidly fastened to two opposed end walls of a laser housing; the electrodes are also rigidly fastened to one end wall, the reference plane, while in contrast on the opposite end wall they are held movably in the direction of the discharge gap by one or more alignment pins.